This invention relates to optical transmission systems and, more particularly, to performance optimization of optical channels in optical transmission systems.
Optical transmission systems and, especially, those employing Wavelength Division Multiplexing (WDM) are desirable because they provide extremely wide bandwidths for communications channels. Each communications channel in the WDM transmission system carries a plurality of optical channels, i.e., wavelengths, on a single optical fiber and single optical repeater. However, there is a trade off between providing wider bandwidth communications channels, with their lower cost of transport, and their vulnerability to channel impairments or the like that corrupt the quality of transmission. Therefore, the ability of an optical transmission system, for example, those employing WDM, to minimize the effects of channel impairments and other signal corrupting mechanisms on the optical communications services is extremely important.
Vulnerability of an optical network to channel impairments or the like, is addressed by utilizing real-time monitoring and control of one or more prescribed optical channel impairments. The one or more impairments are compensated for by employing an optimization process in the optical network such that the optical signals from the source or sources of the impairments are controllably adjusted at any particular node in the network. In a specific embodiment of the invention, the optical signals are attenuated more or less at the source node of the associated optical channel, e.g., wavelength xcex, in order to optimize performance of the corresponding optical channel in the network. This is realized by employing a variable optical attenuator at the xcex laser source of optical channel having the impairment.
More specifically, in a particular embodiment of the invention, the optical signal impairment is measured at a receiving node and the source node of the associated optical channel is determined. Then, a control message is transmitted to the identified source node indicating that a variable optical attenuator associated with the corresponding optical channel light source, e.g., xcex laser source, is to be adjusted to insert more or less attenuation as the case may be. This measurement and adjustment process is iterated until the corresponding optical channel yields optimum performance for the impairment being measured. In this embodiment of the invention, the control messages are transmitted in an optical supervisory channel.
In another embodiment of the invention, a VOA in a remote node associated with the xcex laser source of the associated optical channel is first adjusted. Thereafter, if necessary, a VOA in the local node associated with the optical channel being monitored is adjusted to further optimize the prescribed metric of the optical channel being monitored. This adjustment of the local VOA is iterated until the performance of the associated channel is optimized.
In still another embodiment of the invention, either a VOA in a remote node associated the xcex laser source of the associated optical channel adjusted or a VOA at a local node associated with the received prescribed optical channel is adjusted or both VOAs are adjusted depending on an evaluation of the prescribed metric of the prescribed optical channel to optimize the prescribed metric of the prescribed optical channel.
In yet another embodiment of the invention a VOA in a remote node associated the xcex laser source of the associated optical channel adjusted and a VOA at a local node associated with the received prescribed optical channel are substantially simultaneously adjusted to optimize the prescribed metric of the prescribed optical channel.
A technical advantage of the invention is that the transmission performance of the one or more optical channels is optimizes in substantially real time.